Upon improving recording density of thin-film magnetic heads, it is important to form a narrow main pole layer (recording magnetic pole film) so as to concentrate recording magnetic flux on a recording medium and enable writing of magnetic information onto the recording medium. As one example of its manufacturing method, Japanese Unexamined Patent Application Publication No. 2007-257815 discloses a method in which after a resist is applied, exposed and developed by a photolithography process to form a resist pattern having an opening, a recording magnetic pole film is formed in the opening.
During the exposure upon the formation of the resist pattern, however, a reflected light from a base generates a stationary wave with an incident light to cause roughness on side faces of the resist opening to be used for formation of the recording magnetic pole film, which becomes a big problem in a recording magnetic pole film formation process that requires accurate control of size and shape.